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PubMed1981

Species difference in N-hydroxylation of a tryptophan pyrolysis product in relation to mutagenic activation.

Metabolic activation of a tryptophan pyrolysate, 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2), in liver microsomes from rats, mice, hamsters, guinea pigs, and rabbits was studied to know whether N-hydroxylation is a common obligatory step for mutagenic activation of Trp-P-2. Among hepatic microsomes obtained from untreated animals, the highest activity of Trp-P-2 N-hydroxylase was observed in microsomes from hamsters, followed by those from guinea pigs, mice, and rabbits. In rats, the activity was low, and there was no appreciable difference between the sexes. The activity of Trp-P-2 N-hydroxylase in microsomes was increased by pretreating the animals with a polychlorinated biphenyl mixture. The induction was most profound in rats, and the activity was enhanced 257-fold, as compared to that of untreated animals. The activity was also enhanced in microsomes from polychlorinated biphenyl mixture-treated rabbits, mice, and hamsters, while the activity was increased only slightly in guinea pigs and was thereby lowest among microsomes from the polychlorinated biphenyl mixture-treated animals. In bacterial mutagenesis test systems using Salmonella typhimurium TA 98, the number of revertants induced by Trp-P-2 was increased in parallel with the microsomal ability of the N-hydroxylation. These results indicate that in all species examined N-hydroxylation is an essential metabolic step for mutagenic activation of Trp-P-2.

Animals↗
PubMed1995

Airway smooth muscle relaxant effects of the cocaine pyrolysis product, methylecgonidine.

Methylecgonidine (anhydroecgonine methylester; MEG) is produced when cocaine base ("crack") is heated. Since crack smoking can produce significant airway toxicity and the role of MEG in this toxicity is unknown, we determined the effects of MEG on guinea pig isolated tracheal rings. Trachea do not contract in response to MEG; rather, MEG (10(-9) to 10(-3) M) dose-dependently relaxed tissue precontracted with 2 x 10(-3) M acetylcholine (ACh). MEG (10(-9) to 10(-6) M) reduced the magnitude of contractions induced by ACh, carbachol, histamine and KCl in a nonsurmountable manner; the maximal response to these agents was not restored after repeated washing. MEG did not affect contractions induced by BaCl2. 4-Diphenyl acetoxymethyl piperidine methiodide (4-DAMP; 10(-7) M), in the presence or absence of MEG (10(-7) M), shifted the dose-effect curve for ACh 30-fold to the right. After washing, sensitivity to ACh was fully recovered in tissues exposed to 4-DAMP alone, but was still reduced to 50% of control in tissues exposed to 4-DAMP and MEG. The effects of MEG were unlike those of cocaine which, at 10(-7) to 10(-5) M, increased the magnitude of contractions induced by ACh (10(-9) to 2 x 10(-3) M); MEG (10(-7) M) abolished this increase. The mechanism by which MEG relaxes tracheal smooth muscle has not been established, but it is likely to be independent of direct interaction with sites that mediate the effects of the bronchoconstrictor agents used in this study.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMedDate not supplied

Polymer fume fever and other fluorocarbon pyrolysis-related syndromes.

Polymer fume fever usually occurs as a self-limited systemic illness with only minor pulmonary symptoms. Like metal fume fever, constitutional signs and symptoms typically present several hours after initial exposure, often giving rise to a misdiagnosis of viral "flu." Compared to metal fume fever, polymer fume fever has a more varied clinical presentation, the severity of which depends upon the specific conditions of exposure. When higher temperatures and/or longer durations of exposure are involved, significant pulmonary involvement, including radiographic consolidation, is a potential complication. Although a number of industrial outbreaks have implicated the smoking of contaminated cigarettes as a vehicle of exposure, any industrial or household activity in which PTFE is heated above 350-400 degrees C puts nearby workers or residents at risk of illness and is to be avoided without strict industrial hygiene controls.

Animals↗
PubMed2004

An overview of the effects of tobacco ingredients on smoke chemistry and toxicity.

This paper presents an overview of a series of studies designed to assess the influence of 482 tobacco ingredients on cigarette smoke chemistry and toxicity. The studies are: pyrolysis of the ingredients; influence of the ingredients on smoke constituents believed by regulatory authorities to be relevant to smoking-related diseases ("Hoffmann analytes"); influence of the ingredients on in vitro genotoxicity and cytotoxicity of smoke partiulate matter; and influence of the ingredients on the inhalation toxicity of smoke. The present paper brings the salient features of these studies together. A pyrolysis technique has been developed which, as far as practicably possible, mimics the combustion conditions inside a burning cigarette. The results from 291 single-substance ingredients indicate that almost a third would transfer out of the cigarette burning zone at least 99% intact (i.e. less than 1% pyrolysis), and almost two thirds would transfer at least 95% intact. Of the ingredients that underwent some degree of pyrolysis, a few "Hoffmann analytes" were detected amongst the pyrolysis products of 19 ingredients. Taking into account maximum use levels, their maximum pyrolysis levels were generally small and often insignificant compared to the levels typically present in smoke. Possible exceptions were acetaldehyde and benzene from the pyrolysis of malic acid. However, subsequent smoke chemistry studies indicated that the maximum levels predicted from pyrolysis of this involatile substance were overestimated, suggesting that malic acid does not undergo complete pyrolysis in the burning cigarette and/or generates acetaldehyde and benzene at similar rates to that of tobacco on a per weight basis. When added to tobacco, many of the ingredient mixtures produced no significant effect on the levels of many of the "Hoffmann analytes" in smoke, while some produced increases or decreases relative to the relevant control cigarettes. The study has concentrated on the increases. Many of the differences were found to be not significant when the long-term variability of the analytical methodology was taken into account. However, even taking this into account, the smoke formaldehyde levels in two of the test cigarettes were significantly increased relative to their controls, by up to 26 microg (73%). These increases are likely to be due to the pyrolysis of sugars, cellulose and other polysaccharide materials. The activity of smoke particulate matter from cigarettes containing tobacco ingredients has been determined with three in vitro bioassays, two for genotoxicity and one for cytotoxicity. These were the Ames test, the mammalian cell micronucleus assay, and the neutral red uptake cytotoxicity assay. Within the sensitivity and specificity of these bioassays, the specific activity of the cigarette smoke particulate matter was not changed by the addition of ingredients to the cigarette. Three 90-day sub-chronic inhalation studies have been undertaken and histopathological and histomorphometric assessments made within the respiratory tracts of animals exposed to smoke from cigarettes containing the various ingredient mixtures and their control cigarettes. The response due to tobacco smoke exposure was not distinguishable between the test and control cigarettes, indicating that the presence of the ingredients had made no discernable differences to the type and severity of the treatment-related changes.

Administration, Inhalation↗
PubMed1996

Recognition of chitin and proteins in invertebrate cuticles using analytical pyrolysis/gas chromatography and pyrolysis/gas chromatography/mass spectrometry.

Flash pyrolysis/gas chromatography (py/GC) and py/GC/mass spectrometry (MS) have been utilized to characterize the cuticles of invertebrates chemically. Pyrolysis products have been identified and assigned to specific cuticular components. Acetylpyridones, acetamidofuran, 3-acetamido-5-methylfuran and 3-acetamido-(2 and 4)-pyrones are proposed as characteristic pyrolysis markers for chitin. Pyrolysis products displaying ions of m/z 70, 154, 168, 194 are thought to derive from diketopiperazine structures and provide potential markers for proteins and peptides in which proline, alanine, valine, arginine and glycine are the dominant amino acids. These products, constituting specific pyrolysis markers for invertebrate cuticles, may reflect the amino acid composition of their constituent structural proteins. The source of the various pyrolysis products of proteins has been verified by pyrolysis of reference proteins, peptides and amino acid mixtures. The presence of additional pyrolysis products related directly to histidine and catechol moieties is consistent with the chemical structure and composition proposed for arthropod cuticles based on recent work utilizing solid state 13C and 15N nuclear magnetic resonance. This study constitutes the first comprehensive chemical characterization of the pyrolysis products of invertebrate cuticles and provides the basis for future investigations requiring qualitative screening for cross-linked chitin and proteins in modern and fossil cuticles and in materials, e.g. geopolymers, that may be derived from them.

Animals↗
PubMed1999

Molecular insight into soil carbon turnover.

Curie-point pyrolysis-gas chromatography coupled on-line to mass spectrometry (Py-GC/MS) and isotope ratio mass spectrometry (Py-GC/IRMS) were used to determine the individual turnover rate of specific carbohydrates, lignin, lipids and N-containing compounds from French arable soils. The analysed soils were cultivated, either continuously with a C3 plant (wheat delta(13)C-value = -25.2 per thousand), or transferred to a C4 plant (maize delta(13)C-value = -11.4 per thousand) cropping 23 years ago. Most pyrolysis products identified were related to carbohydrates (furans), lipids (hydrocarbons and derivatives of benzene), proteins (nitriles and pyrrole) and lignins (phenols). The relative yield of all individual pyrolysis products was similar in the samples from the maize and control wheat soil. The isotopic enrichment between identical pyrolysis products from the two soils varied from 1 to 12 delta (delta) units, indicating that after 23 years of cultivation 7 to 90% of their C was derived from maize. This suggests a slow mean turnover time varying from 9 to 220 years. Based on the differences in isotopic enrichment of chemical structures after vegetation change the pyrolysis products could be divided into three groups: (i) pyrolysis products with a nearly complete C4 signal, e. g. phenol, derived from lignin degradation products, (ii) pyrolysis products with an intermediate isotopic enrichment of 6-8 per thousand, most likely to be a composite of remaining (possibly physically protected) fragments derived from both maize and native wheat, and (iii) pyrolysis products showing only low enrichments in (13)C of 1-3 per thousand. Most of their precursors were found to be proteinaceaous materials. This indicates that proteins or peptides are indeed preserved during decomposition and humification processes occurring in the soil. Our study highlights the potential of Py-GC/MS-C-IRMS to further novel insights into the dynamics of soil organic constituents. Copyright 1999 John Wiley & Sons, Ltd.

Journal Article↗
PubMed2004

Investigations into the pyrolytic behaviour of coal/biomass blends using thermogravimetric analysis.

Investigations into the pyrolytic behaviour during co-pyrolysis of coal, biomass materials and coal/biomass blends prepared at different ratios (10:90, 20:80, 30:70 and 50:50) have been conducted using a thermogravimetric analysis (TGA) apparatus. The coal sample selected was Collie sub-bituminous coal from Western Australia, while wood waste (WW) and wheat straw (WS) were used as biomass samples. Three thermal events were identified during the pyrolysis. The first two were dominated by the biomass pyrolysis, while the third was linked to the coal pyrolysis, which occurred at much higher temperatures. No interactions were seen between the coal and biomass during co-pyrolysis. The pyrolytic characteristics of the blends followed those of the parent fuels in an additive manner. Among the tested blends, 20:80 blends showed the lowest activation energies of 90.9 and 78.7 kJmol(-1) for coal/WW and coal/WS blends respectively. The optimum blend ratio for pyrolysis of coal/WS was 50:50 with a high degradation rate in all the thermal events and a higher mass loss over the course of the co-pyrolysis compared to coal/WW blends examined. The reaction orders in these experiments were in the range of 0.21-1.60, thus having a significant effect on the overall reaction rate. Besides the pyrolysis of coal alone, the 50:50 coal/biomass blends had the highest reaction rate, ranging 1x10(9)-2x10(9) min(-1). The experimental results may provide useful data for power generation industries for the development of co-firing options with biomass.

Australia↗
PubMed2001

Production of monomeric phenols by thermochemical conversion of biomass: a review.

Biomass is a renewable and alternative source for the production of fuels and chemicals. This paper provides a brief survey of lignin precursors as well as thermogravimetric and pyrolysis studies of lignin with special reference to the production of phenols. Thermogravimetric analysis provides information on pyrolysis kinetics while thermogravimetry in combination with mass or infrared spectrometers allowed a rapid characterization of the vapours produced by thermal treatment. Pyrolysis enabled even greater insight into the thermal behaviour of lignin. Pyrolysis of single, dimeric and trimeric model lignin compounds can determine the thermal stability of the intermediate compounds formed and the origin of the pyrolysis products. A free radical mechanism has been suggested as a major route during the early lignin degradation stages followed by a combined free radical and concerted pathway at elevated temperatures. Pyrolysis of lignin in the presence of catalysts as additives was investigated. Significant differences in terms of yields of pyrolysis products and phenolic compounds were observed. The addition of salts resulted in a high weight loss at low temperature and yielded more char than untreated wood. Some metal catalysts such as transition metals and metal oxides such as Fe2O3 and Cu exhibited a better activity in terms of selectivity for the degradation of lignin.

Biomass↗
PubMed2006

A study of the fiber obtained from the water bamboo husks.

The water bamboo husks are the main agricultural wastes of Taiwan in summer. In this study, the fiber obtained from the water bamboo husks was investigated by CP/MAS C13 NMR, elemental analysis, and adiabatic calorimeter. Moreover, the pyrolysis behavior of the fiber was studied by TGA, TGA-GC-MS and Py-GC-MS. The kinetic parameters of the pyrolysis process of the fiber were calculated by the modified Kilzer-Broido model, Coats and Redfern method, Harcourt and Esson relationship, and Ozawa method, respectively. The results imply that the fiber is cellulose I type. Moreover, the kinetic analysis reveals that the pyrolysis of the fiber in nitrogen is more likely to be the model D3 mechanism. However, the pyrolysis of the fiber in air is much more complicated and the activation energies of pyrolysis are quite different from those in nitrogen. Based on the TGA-GC-MS and Py-GC-MS study, the decomposed products from the pyrolysis of the fiber are of interest for their potential use as organic resources.

Cellulose↗
PubMed1999

Comparison of the cytotoxic and mutagenic potential of liquid smoke food flavourings, cigarette smoke condensate and wood smoke condensate.

Although products of pyrolysis are often cytotoxic and mutagenic, the relationship between the type of material pyrolysed and the toxicity of the resulting pyrolysis products is poorly understood. The objective of this study was to evaluate and compare the cytotoxicity and mutagenicity of several types of common pyrolysis products. The cytotoxicity and mutagenicity of these products were assessed by using neutral red uptake and Ames mutagenicity assays, respectively. The biological activities of four liquid smoke food flavourings (LSF) were compared with two other pyrolysis-derived materials; cigarette smoke condensate (CSC) and a wood smoke condensate (WSC). Results indicated all of the mixtures exhibited a concentration-dependent cytotoxic response. The CSC and WSC were less cytotoxic than three of the LSFs, but more cytotoxic than one of the brands. The CSC was mutagenic in two Salmonella strains; however, none of the LSFs or WSC was mutagenic using TA98, and only three of the LSFs were positive with TA100. The six pyrolysis-derived materials evaluated in this study showed differing patterns and magnitudes of cytotoxicity and mutagenicity. These results indicate that the cytotoxicity and mutagenicity of complex mixtures derived from pyrolysis products are affected by the type of material pyrolysed and/or the method used to prepare the mixture. The cytotoxic potential of some commercial smoke flavourings is greater than cigarette smoke condensate and several of the food flavourings are mutagenic in one Salmonella strain.

Animals↗
PubMed1990

Free radical formation by ultrasound in aqueous solutions. A spin trapping study.

Our recent spin trapping studies of free radical generation by ultrasound in aqueous solutions are reviewed. The very high temperatures and pressures induced by acoustic cavitation in collapsing gas bubbles in aqueous solutions exposed to ultrasound lead to the thermal dissociation of water vapor into H atoms and OH radicals. Their formation has been confirmed by spin trapping. Sonochemical reactions occur in the gas phase (pyrolysis reactions), in the gas-liquid interfacial region, and in the bulk of the solution (radiation-chemistry reactions). The high temperature gradients in the interfacial regions lead to pyrolysis products from non-volatile solutes present at sufficiently high concentrations. The sonochemically generated radicals from carboxylic acids, amino acids, dipeptides, sugars, pyrimidine bases, nucleosides and nucleotides were identified by spin trapping with the non-volatile spin trap 3,5-dibromo-2,6-dideuterio-4-nitrosobenzenesulfonate. At low concentrations of the non-volatile solutes, the spin-trapped radicals produced by sonolysis are due to H atom and OH radical reactions. At higher concentrations of these non-volatile solutes, sonolysis leads to the formation of additional radicals due to pyrolysis processes (typically methyl radicals). A preferred localization of non-volatile surfactants (compared to analogous non-surfactant solutes) was demonstrated by the detection of pyrolysis radicals at 500-fold lower concentrations. Pyrolysis radicals were also found in the sonolysis of aqueous solutions containing only certain nitrone spin traps. The more hydrophobic the spin trap, the lower the concentration at which the pyrolysis radicals can be observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Electron Spin Resonance Spectroscopy↗
PubMed1987

The role of minerals in the thermal alteration of organic matter--IV. Generation of n-alkanes, acyclic isoprenoids, and alkenes in laboratory experiments.

A series of pyrolysis experiments, utilizing two different immature oil-prone kerogens ("type I": Green River Formation kerogen; "Type II": Monterey Formation kerogen) mixed with common sedimentary minerals (calcite, illite, or Na-montmorillonite), was conducted to study the effects of minerals on the generation of n-alkanes, acyclic isoprenoids, and alkenes during laboratory-simulated catagenesis of kerogen. The influence of clay minerals on the aliphatic hydrocarbons is critically dependent on the water concentration during laboratory thermal maturation. Under extremely low contents of water (i.e., dry pyrolysis, where only pyrolysate water is present), C12(+) -range n-alkanes and acyclic isoprenoids are mostly destroyed by montmorillonite but undergo only minor alteration with illite. Both clay minerals significantly reduce alkene formation during dry pyrolysis. Under hydrous conditions (mineral/water = 2:1), the effects of the clay minerals are substantially reduced. In addition, the dry pyrolysis experiments show that illite and montmorillonite preferentially retain large amounts of the polar constituents of bitumen, but not n-alkanes or acyclic isoprenoids. Therefore, bitumen fractionation according to polarity differences occurs in the presence of these clay minerals. By this process, n-alkanes and acyclic isoprenoids are concentrated in the bitumen fraction that is not strongly adsorbed on the clay matrices. The extent of these concentrations effects is greatly diminished during hydrous pyrolysis. In contrast, calcite has no significant influence on the thermal evolution of the hydrocarbons. In addition, calcite is incapable of retaining bitumen. Therefore, the fractionation of n-alkanes or acyclic isoprenoids relative to the polar constituents of bitumen is insignificant in the presence of calcite.

Alkanes↗